Can a Remington wingmaster 870 pump bought in 1967 be used with the steel shot shells of today?

Would probably not suggest that. You can check with Remington customer service through their website for a definite answer. Additional barrels that CAN handle steel shot are available.

Here's why it's NOT a good idea to use "steel shot" in your 1967 Remington Model 870 barrel. On the older shotguns the forcing cone (just ahead of the chamber) has a 5-degree 45-minute angle that's only around 3/8-inch long, and the bore is .729 in diameter. With the sharp angle of the forcing cone the steel shot will pound against that shoulder and most likely peen it away. There were still quite a few shotshells (lead pellets) that used the fiber style of wadding between the shot and the gunpowder in use back then, so the forcing cone needed to be a short, abrupt angle so that the wad could seal the gasses from the burning shotshell powder. These days, we have plastic shot-cups that hold the steel shot and then they have a skirt on the back end of the wad to seal the burning powder and gasses at the moment of ignition. Much more efficient. Also, modern shotguns have back-bored barrel bores, chrome plated for steel, that measure .735 in diameter with forcing cones that are much longer (around one and three quarter inch long) with a 1-degree 30 minute angle forcing cone that transitions the shot into the barrel more gradually. If you were to shoot steel shot out of your vintage 1967 barrel with its softer steel, you will most likely peen the choke constriction out of it.